In the fabrication of certain types of containers, particularly wide-mouth containers, it is conventional practice to blow mold an intermediate container product from a preform, and then to remove the upper portion of the intermediate product, referred to as a dome or moil, in a post-molding operation. U.S. Pat. No. 4,576,843 discloses a container manufacturing method of this type, in which the moil is removed by knife blades carried by the blow mold sections. It has also been proposed to fabricate containers of the subject type having a multilayer or laminated sidewall that includes one or more intermediate layers of barrier resin such as ethylene vinyl alcohol (EVOH) or nylon. U.S. Pat. No. 4,550,043, for example, discloses a process for making a preform for such a container, in which the intermediate barrier layer can be controlled to extend only part-way through the preform and the intermediate container product.
Problems are encountered when making containers of this type. For example, it is difficult to control placement of the edge of the intermediate barrier layer exactly at the moil trim line, so that the barrier layer must be made to extend into the moil to ensure that the barrier layer extends throughout the final container product. This, however, compromises the ability to use the trimmed moil as process regrind inasmuch as it is undesirable to have barrier material in the process regrind. Furthermore, the use of knife blades to trim a multilayer container product is undesirable because the blade can cause delamination at the trim line, and because the knife blade is subject to excessive wear when used in combination with abrasive container layer materials such as polyethylene terephthalate (PET). U.S. Pat. No. 4,549,066 discloses the use of a laser for performing the trimming operation, which reduces the delamination and wear problems.
A method making a plastic container in accordance with one aspect of the present invention includes molding an intermediate container product having a body and a moil integral with the body. The body is of layered construction that includes at least one layer of barrier resin that extends part-way into but not throughout the moil. The upper portion of the moil, in which the barrier material is absent, is removed for recycling as process regrind. The lower portion of the moil is removed to form the container. In the preferred embodiment of the invention, the upper portion of the moil is removed in a laser trimming operation. The lower portion of the moil is removed in the preferred embodiment of the invention by inserting a plug into the open end or mouth of the container, and employing a cutting tool that is positioned by the plug for accurately trimming the container product with respect to the mouth of the container. The cutting tool preferably is either a pair of shear rollers or a laser cutting tool.